1. Field of the Invention
The present invention relates to a tilt-swivel stand. In particular, it relates to a tilt-swivel stand to support e.g. a CRT (cathode ray tube) for moving the screen of the CRT both in a vertical plane (tilt) and in a horizontal plane (swivel).
2. Description of the Related Art
An example of conventional tilt-swivel stands is disclosed in JP-A-6(1994)-189229. The conventional stand, as shown in FIG. 10 of the accompanying drawings, is provided with a base 50 placed on e.g. a desk, and a movable member 60 upon which a CRT is mounted.
The base 50 is provided at its upper portion with a concave supporting surface 51 coinciding with a part of the surface of a sphere. An upright protrusion 52 extends at the center of the support surface 51. The movable member 60 is provided at its lower portion with a convex slide surface 61 whose curvature is equal to that of the above-mentioned concave surface 51. The slide surface 61 is formed with an elongated guide groove 62 to receive the protrusion 52 of the base 50. The width of the groove 62 is slightly greater than the outer diameter of the protrusion 52.
In the assembled state, the concave surface 51 is held in sliding engagement with the convex slide surface 61, with the protrusion 52 extending into the guide groove 62. A screw 70 with a sufficiently large head is driven into the upper portion of the protrusion 52 to prevent the movable member 60 from coming off the base 50.
With the above arrangement, the movable member 60 is still allowed to tilt on the base 50 as the protrusion 52 is moved along the groove 62. Also, the movable member 60 can be swiveled about the protrusion 52 with respect to the base 50, at whatever position the protrusion 30 is located within the guide groove 62.
However, in the conventional tilt-swivel stand, the screw 70 is used for holding the base 50 and the movable member 60 together. Unfavorably, driving the screw 70 into the prescribed portion requires for an additional procedure in the assembly line. Also, to use the screw 70 will raise the production costs.
Another example of conventional tilt-swivel stands is disclosed in JP-A-8(1996)-140017. As shown in FIG. 11 of the accompanying drawings, the conventional stand includes a base (not shown) and a movable member 80 held in sliding engagement with the base, as in the previous conventional stand (FIG. 10). The tilt-swivel stand of FIG. 11 is different from the previous one in that no screw is used for attaching the movable member 80 to the base.
Specifically, as shown in FIG. 11, an upright protrusion 90 is arranged at the center of the base, and a guide groove 81 is formed in the movable member 80 for receiving the upright protrusion 90. The upright protrusion 90 is formed with several fins 90a projecting radially. The guide groove 81 has a uniform width except for one end 81a at which a generally circular through-hole is formed.
For attaching the movable member 80 to the non-illustrated base, the protrusion 90 is inserted into the guide groove 81 at the enlarged end 81a. The end 81a is large enough to allow the fins 90a to go beyond the groove 81. Then, the movable member 80 is caused to slide on the base, so that the fins 90a are moved from the end 81a to the constant-width portion 81b, as shown in FIG. 11. In this state, some of the horizontally projecting pins 90a are caught by the movable member 80, thereby securing the movable member 80 to the non-illustrated base.
With such an arrangement, no additional fixing means such as a screw is needed, which is advantageous to reducing the number of parts necessary for assembling the tilt-swivel stand. Consequently, the production costs and production time are both reduced.
Though the tilt-swivel stand of FIG. 11 has the above advantages, it has been found disadvantageous in the following point.
As long as the protrusion 90 is located in the constant-width portion 81b of the groove 81, the movable member 80 is prevented from coming off the non-illustrated base due to the fins 90a abutting on the movable member 80. However, the protrusion 90 may be brought to the enlarged portion 81a of the groove 81 when the user tilts the CRT mounted on the movable member 80 too much. This unusual positioning of the protrusion 90 relative to the groove 81 is invisible to the user since an CRT is placed on the movable member 80. Thus, unaware of the current situation, the user may try to move the CRT to a different location and lift it. However, with the stopping fins 90a located at the enlarged portion 81a of the groove, the non-illustrated base may come off the movable member 80 and may fall onto the desk.
The present invention has been proposed under the circumstances described above, and its object is to provide a tilt-swivel stand which can be readily assembled and does not suffer from accidental detachment of the movable member from the base.
According to the present invention, there is provided a tilt-swivel stand including: a base member provided with a concave surface having a predetermined curvature; a movable member mounted on the base member and provided with a convex surface having a curvature equal to the curvature of the concave surface; and connecting means for connecting the base member to the movable member. The connecting means includes a protrusion and a guide groove which has a predetermined width. The protrusion includes a shank and an engaging portion which has a normal size greater than the width of the guide groove. The engaging portion is flexible enough to go through the guide groove.
With such an arrangement, the movable member is readily attached to the base member simply by pressing the protrusion into the guide groove. The flexible engaging portion is reduced in overall size as it is going through the guide groove, and then restores on its own to the original shape after passing by the guide groove. In this position, the engaging portion is caught by the member in which the guide groove is formed (that is, the movable member or base member), thereby holding together the movable member and the base member.
In the assembled state, the movable member is mounted on the base member, with the convex surface of the former held in sliding engagement with the concave surface of the latter. The guide groove into which the protrusion is inserted for restriction of movement is typically straight, thereby allowing the movable member to move in a vertical plane (that is, xe2x80x9ctiltxe2x80x9d) relative to the base member. How far the movable member can be tilted depends upon the length of the guide groove.
Though the tilting movement is restricted by the configuration of the guide groove, as stated above, basically the rotation of the protrusion relative to the guide groove is not limited by the geometry of the groove. This means that rotation of the protrusion relative to the guide groove can take place at any position in the groove.
According to a preferred embodiment of the present invention, the shank of the protrusion includes a diametrically larger portion and a diametrically smaller portion. The diametrically larger portion is substantially equal in size to the width of the guide groove.
With such an arrangement, the protrusion is properly guided by the guide groove when the diametrically larger portion of the protrusion is held in the guide groove.
According to a preferred embodiment of the present invention, the protrusion is provided on the movable member, while the guide groove is provided on the base member.
Alternatively, the protrusion may be provided on the base member, while the guide groove may be provided on the movable member.
Preferably, the protrusion may have an anchor-like configuration. Specifically, the engaging portion may include a pair of engaging pieces which are non-parallel to each other. Each of the engaging pieces may be a generally rectangular plate, though the present invention is not limited to this.
The tilt-swivel stand of the present invention may further includes stopping means for restricting rotation of the movable member relative to the base member. Preferably, the stopping means may include a profiled element and a stopping wall. The profiled element may be arranged adjacent to the protrusion, while the stopping wall may be arranged adjacent to the guide groove.
Preferably, the profiled element may be provided with a generally rectangular portion and a semi-cylindrical portion.